Two-stroke cycle internal combustion engine



Aug. J41; 1937. w. M CLELLAND TWO-STROKE CYCLE INTERNAL COMBUSTIONENGINE 4 Sheets-Sheet 1 Filed May 9, 1935 m if [17175277175 M'f/[aZia/555120 TWO-STROKE CYCLE INTERNAL COMBUSTION ENGINE Filed May 9, 19354 Sheets-Sheet 2 Int an TO}? I MZ/[EZU maize/[727d g- 1937 w. MOCLELLAND2,088,863

TWO-STROKE CYCLE INTERNAL COMBUSTION ENGINE Filed May 9, 1935 4 Sheets-Sheet 3 INVENTUE Aug. 3, 1937.

w. MCCLELLAND 2,088,863 TWO-STROKE CYCLE INTERNAL COMBUSTION ENGINEFiled May 9, 1935 4 Sheets-Sheet 4 1771725777275 [Mi/1am 2775575151 57 53' UNITED STATES TWO-STROKE CYCLE INTERNAL COMBUS- TION ENGINE WilliamMcClelland, Rock Fen-y,,Birkenhead, England Application May 9, 1935,Serial No. 20,695 In Great Britain May 11, 1934 Claim.

This invention is for improvements in or relating to internal combustionengines of the kind adapted to operate on the two-stroke cycle. Theinvention is applicable to engines fired by a spark 5 or the like or tocompression-ignitionengines.

Among the objects of the present invention are to provide an engine ofthe above kind in which the mass of the moving parts is balanced aboutthe axis of rotation of the engine so as to minimize as far as possibleengine vibration, and in addition to provide a two-stroke engine inwhich the combustible fuel or a component thereof is positively driveninto the working cylinder.

Accordingly the present invention provides an internal combustion engineof the kind described comprising in combination a crank case, a crankshaft supported within the crank case so as to be rotatable relativelythereto, at least two powercylinders mounted on the crank case, at least20 two pump-cylinders also mounted on the crank case, a power piston ineach power cylinder and a pump piston in each pump cylinder operativelyconnected to the crank shaft wherein the pistons and their respectiveconnecting rods are of substantially equal mass, and wherein the pistonsare so connected to the crank shaft that each power piston has abalancing pump piston substantially diametrically opposite thereto, andmoving 180 out of phase therewith, whereby the power piston and itsbalancing pump piston are always at the same distance from the crankshaft axis, and wherein each pump piston serves to charge the cylinderof a neighboring power piston with a combustible mixture or a componentthereof. Preferably each power piston is provided with a skirt having aninlet port which can be brought into register with an inlet port in thepower cylinder, whereby a piston in the neighboring pump cylinderconnected to the power cylinder inlet port can be used to draw a chargethrough the ports in the skirt and power cylinder into the neighboringpump cylinder, and expel the said charge into the combustion chamber ofthe power cylinder by way of the power-cylinder inlet port. The port inthe skirt of the power piston can be made of such a size that theneighboring pump piston is drawing a charge into its cylinder duringsubstantially the whole of its suction stroke, whereby an adequatecharge can be expelled into the power cylinder combustion chamber duringreverse movement of the neighboring pump piston. The invention isconveniently applied to a six cylinder radial engine wherein the enginehas six power cylinders and six pump cylinders cylinders and three pumpcylinders in each bank, the power and pump cylinders being alternatelydisposed around the crank case, and wherein all the power pistons areconnected to one crank pin of the crank shaft and wherein the three pumppistons of one bank and the three pump pistons of the other bank arerespectively connected to crank pins located on either side of the crankpin of the power pistons. This arrangement of a six-cylinder engineprovides a good timing with no crank case compression, and the explosivemixture is positively moved during the working of the engine.Furthermore, the crank shaft can be short and stifi and the whole engineis well' balanced.

If desired the connecting rods for all the pistons may have their bigends of segmental shape flanged outwards so that a loose-mounted ringcan couple these ends to a crank pin, that is to say the segmentalshaped cheeks of the connecting rod are sandwiched between theloosemounted sleeve and the crank pin.

Various examples of the invention as applied to engines comprising two,four and six cylinders will now be described with reference to theaccompanying drawings, whereon:--

Figure 1 is a sectional front elevation of a six-cylinder radial engine,the section being taken on the line I--I of Figure 2, looking in thedirection of the arrow.

Figure 2 is an immediate-section side elevation on the line IIII ofFigure 1,

1 Figure 3 is a diagrammatic sectional side elevation of a six-cylinderradial engine having a modified arrangement for coupling the pistons tothe crank shaft.

Figure 4 is a developed plan view of the crank case of the engine shownin Figure 3,

Figures 5 and 6 are diagrammatic front and side elevation respectivelyof a two-cylinder engine according to the invention, and

Figures 7 and 8 are diagrammatic front and side elevation respectivelyof a four-cylinder engine according to the invention.

With reference to Figures 1 and 2, the sixcylinder engine is arranged towork on the twostroke cycle, and comprises two banks of power cylinders,one bank I (la, Hlb, I00, and a second cylinders Illa, I01), I00. Bothbanks of cylinders arranged at 120 radially of the crank shaft axis ineach bank, but the cylinders in the second bank are arranged at aninclination of 60? to the cylinders in, ilib, Hie. Both banks ofcylinders are similarly constructed, and therefore the detaileddescription of one bank with reference to Figures 1 and 2 will apply tothe second bank. The power cylinders Illa, IOb, Illc are associated withthree pump cylinders I2a,- l2b, I2c so that power and pump cylinders arearranged alternately round the crank case. A similar bank of pumpcylinders is associated with the second bank of power cylinders, and onesuch pump cylinder I3c is shown in Figure 2. The crank case I4 is ofhexagonal shape, and the pump cylinders and power cylinders are mountedon the case l4 radially round a crank-shaft I! which is of the two-throwtype and is rotatably supported in bearings I6 on the'crank case. Thepower pistons in both banks are connected to the 15 center crank pin I1and the three pump pistons of each bank are respectively connected tocrank pins l8, I9, on either side of the center crank pin ll. As isusual with engines working on the two-stroke cycle, the explosive.mixture enters the crank case l4 by way of the port 20 controlled by aspring loaded non-return valve 20a.

The power pistons 2Ia, 2") and He are of the normal deflector type withthe exception that the port 22 in the skirt of the piston operates inconjunction with a port 23 in the power cylinders Illa, Iflb and Illewhich communicates by way of the conduit 24 with the neighboring pumpcylinders I2a, I21) and I2c into which a combustible charge is drawnthrough the port 22 as will be described later. The connecting rods ofthe power pistons are coupled to the crank pin I! by means of a splitring 25 which bears on segmental shaped cheeks 26 on the connecting rods21 to hold these rods on to the crank pin I'I. Rings similar to therings 25 serve to hold the pump-piston connecting-rods 28, 29 to thecrankpins IS, IS. The pump pistons 30a, 30b, 30c and the power pistons2la, 2Ib, 2Ic are all of the same mass, and so are the connecting rodsfor -10 each pump piston and power piston. Since,

therefore, the crank shaft is of the two-throw type the pump pistonsbeing all connected to one throw, and the power pistons to the otherthrow,

it will be seen that each power piston has, dia- 45 metrically oppositeto it as in Figure 1, a pump piston moving with the same velocity in theopposite direction so that radially about the axis of the crank shaftthe mass of the moving parts of the engine is balanced.

The pump pistons have, however, a function additional to balancing, andthis function is to serve as a positive charging-means for theneighboring power cylinder, to which the pump piston is connected. Forinstance, with reference to the 55 power cylinder Illa and the pump I2ait will be seen that when the power piston 2la is at the top of itsstroke in the firing position the neighboring pump piston 30a is at thebottom of its stroke, and has drawn an adequate charge for 60 the powercylinder through the port 22 by way of the conduit 24 into the pumpcylinder I2a. When the power piston is on its working stroke it uncoversthe exhaust port 3Ia and later uncovers the inlet port 23 and duringthis period 65 the pump piston 30a is moving at its maximum velocity andforces a full charge into the cylinder Illa.

With the parts in their position illustrated in Figure 2 the piston 2Ia.is in the firing position; 70 piston 2 lb is commencing to compress thecharge;

piston 2 I is completing the firing stroke and the exhaust port is aboutto open. Pump piston 30a is drawing a charge into the pump cylinder I2afrom the crank case through port 23 and conduit 75 24; pump piston 301)has just completed pumping its charge through its associated port 23 andconduit 24 to cylinder lob and pump piston 300 is commencing to pump acharge to power cylinder I I0. The operations described with referenceto the bank of cylinders Illa, IOb and I00 and pumps I2a, I21), and Heare exactly similar in the bank of power cylinders Ila, Ilb, lie and therespective pumps but is 60 out of phase.

The port 22 in the skirts of the power pistons is of such a size thatthe neighbor ng Pump piston can draw a charge into its cylinder by wayof the said port during substantially the whole of the suction stroke ofthat pump piston. In this way an adequate charge for the combustionchambers of the power cylinders is ensured.

The modification shown in Figure 3 is similar in operation to the enginedescribed with reference to Figures 1 and 2, but in this case the crankshaft I has three main bearings 32, 33, and 34, and the pump and powerpistons have the usual big ends strapped around the crank pins so thatthey operate side by side. This necessitates arrangement of the centerlines of the various pistons and cylinders as shown by the chain-dottedlines 36 which are transferred to the developed plan view Figure 4 so asto show how each cylinder is located on the crank-case. Thus, the powercylinder 31 is balanced radially by the pump cylinder 31a and as totorque in relationto the center-bearing 33 by the power cylinder 31!).

In the diagrammatic views Figures 5 and 6 there are two power pistons38, 39 balanced respectively by two pumping pistons 38a, 39a. Theportion of the engine otherwise is the same as described with referenceto Figures 1 and 2:

In Figures 7 and 8 there are four power pistons 40a and 4027 on onecrank pin and two balancing pistons Ma and 4Ib on the other crank pin.This arrangement is duplicated to bring the working cylinders up to 4 aswill be seen in Figure 8.

With the arrangement described for a sixcylinder radial engine there aresix firing strokes per revolution of the crank shaft, thereby giving aneven torque equal to a twelve-cylinder engine operating on thefour-stroke cycle. The overall length of the engine is comparativelysmall, and the crank shaft can be very short and stiff. There is ofcourse no cam shaft and drive and no valves or tappets.

It will be appreciated of course that any of the standard arrangementsinsofar as ignition cooling, lubricating and mounting of the engine maybe adopted. In the case of a compressionignition engine air only wouldbe drawn through the crank case into the pump cylinders, and if desiredthe pump pistons can be made of larger diameter than the power pistons,still being of course of the same weight, thereby giving a thoroughscavenging action by the large blast of air. The fuel would be injectedat the top of each stroke of the power piston with or without suitablearrangements for producing turbulence, otherwise the cycle of operationswill be substantially as herein described.

Furthermore, with the ordinary petrol engine by making the pump pistonof substantially greater diameter than the power piston but of the sameweight a super-charging effect may be produced. The invention is alsoadvantageous when applied to rotary engines. In such cases of course thecrank shaft remains stationary, and the engine casing rotates. For therotary engines the mixture or air can enter the crank case through ahollow crank shaft.

Modifications may be made in the example hereinbefore described withoutdeparting from the nature of the invention as herein defined; forexample, the number of working cylinders used may vary, and the pairingof these cylinders with an appropriate pump may be arranged in anydesired manner. Furthermore the normal master connecting rod andauxiliary connecting rod arrangements may be used to couple the pistonsand the crank shaft. The inside of the conduit 24 connecting the pumpand power cylinders may be provided with a scroll or similar device forproducing turbulence in the gas expelled into the combustion chamber ofthe power cylinder.

What is claimed is:-

1. A two-stroke cycle internal combustion engine, comprising incombination, a crank case, crank shaft bearings on the said crank case,a crank shaft rotatable in said bearings, at least two power unitshaving inlet and exhaust ports, means connecting the said power units tothe crank case, a pump unit diametrically opposite each power unit andhaving suction and discharge ports, a conduit connecting each of thesaid pump units to the crank case, said conduit also connecting thedischarge port of each pump unit to the inlet port of an adjacent powerunit whereby each pump unit serves to charge the cylinder of an adjacentpower unit with a component of a combustible mixture, characterized by apower piston in each power unit, a pump piston in each pump unit, themass of which is equally to that of the opposite power piston, crankpins on the crank shaft, arranged diametrically opposite each other, i.e. 180 out of phase, and of equal throw, and connecting rods of equalmass and length operatively connecting diametrically opposite power andpump pistons to diametrically opposite crank pins so that each powerpiston and its opposite pump piston are at all times during theoperation of the engine, equi-distant from the crank shaft axis, wherebythe engine is balanced dynamically.

2. A two-stroke cycle internal combustion engine comprising incombination a crank case, crank shaft bearings on said crank case, acrank shaft rotatable in said bearings, at least two power units havinginlet and exhaust ports, means connecting the said power units to thecrank case, a pump unit diametrically opposite each power unit andhaving a combined suction and discharge port, a conduit connecting eachof the said pump units to the crank case, said conduit also connectingthe said suction-discharge port of each pump unit to the crank case byway of the inlet 3 port of an adjacent power unit whereby each pump unitserves to draw a component of a combustible mixture from the said crankcase and charge it into the cylinder of the adjacent power unit by wayof the inlet port thereof, characterized by a power piston, in eachpower unit, having a ported skirt controlling the inlet port of the saidpower unit, a pump piston in each pump unit, the mass of which is equalto that of the opposite power piston, crank pins on the crank shaft,arranged diametrically opposite each other, i. e. 180 out of phase, andof equal throw, and connecting rods of equal mass and length operativelyconnecting diametrically opposite power and pump pistons todiametrically opposite crank pins so that each power piston and itsopposite pump piston are, at all times during the operation of theengine, equi-distant from the crank shaft axis, whereby the engine isbalanced dynamically.

3. An internal combustion engine as claimed in claim 2, wherein the sizeof the port in the skirt of the power piston is such that the pumppiston of the adjacent pump unit can draw a charge into its cylinderduring substantially the whole of its suction stroke.

4. An internal combustion engine as claimed in claim 1, and of theradial type, wherein the engine has six power units and six pump unitsarranged in two banks comprising three power units and three pump unitsin each bank, the power and pump units being alternately disposed aroundthe crank case and wherein all the power pistons are connected to onecrank pin of the crank shaft, and wherein the three pump pistons of onebank and the three pump pistons of the other bank are respectivelyconnected to crank pins located at either side of the crank pin of thepower pistons, and 180 out of phase therewith.

5. A two-stroke cycle internal combustion engineas claimed in claim 1,and comprising a plurality of power cylinders and a plurality of pumpcylinders arranged in banks radially around the crank shaft, thecylinders in each bank having their axes in a common plane at rightangles to the crank shaft axis, and wherein the connecting rods of thepower pistons and the pump pistons are provided with segmental big endsand are held on the crank pin by a split ring device whereby the bigends of the connecting rods of each bank of cylinders can be arranged towork on a common portion of a crank pin.

WILLIAM MCCLELLAND.

